Laminated turbine buckets



Feb. 18, 1958 D. GERDAN ETAL 2,823,893

LAMINATED TURBINE BUCKETS Filed June 9, 1952 s sheets-sheet 1.

Attorneys Peb 18, 19548 D. GERDAN ET AL 2,823,893

LAMINATED TURBINE BUCKETS 'Filed June 9, 1952 3 Sheets-Sheet 2 Feb. 18, 1958 D. GERDAN ET AL 2,823,893

LAMINATED TURBINE BUcKETs 3 Sheets-Sheet 3 Filed June 9, 1952 Inventors @fak/f L 17;' f7/1w By Shay-@fai w @f 75%?. p, Attorneys United States Patent @ffice 2,823,893 Patented Feb. 18, 1958 LAMINATED TURBIN E BUCKETS Dimitrius Gerdan and Stuart Wilder, Jr., Indianapolis, Ind., assignors to GeneralMotors- Corporation, Detroit, Mich., a corporation of Delaware Application June 9, 1952, Serial No. 292,546 17 Claims. (Cl. 253--39.15)

limiting the efiiciency and power outputof gas turbines i is the limited temperature of `the motive iiuid imposed by the turbine buckets. Ithas long been realized that adequate pro-vision for [cooling turbine buckets could be beneficial either in increasing the temperature limitation of the engine or in permitting reduced use of critical materials, or both. As a result, many proposals for structures adaptable for cooling have been advanced and some have been used to some extent. Despite the long period of'awareness ofthe need for a satisfactory cooled bucket, progress in this respect has not'been satisfactory.

The principalobjects of ourvinvention` are to provide a turbine bucketor the like having superiory characteristics so far las cooling is concerned; which is off high strength, and, moreover, one which isireadily adapted to simple production techniques.

This result is i' attained by the use of sheet metalfor the major portion, if not all, of the bucket; Aparticular feature of the4 nventnon is the utilization of laminated sheetrmetalconstructionfor the major part of the bucket, the laminae being so disposed as to provide channels for cooling air. The outer surface of the bladepwln'ch is the fluid-directing portion, may be wholly constituted by the edges of the laminae. Alternatively, thevportions of the bladeadjacent the leading` and trailingzedges may bei` defined by folded sheet metal parts or by; solid'strips of a highly heat-resistantalloy. In` any case; the laminated structureprovidesa` strong, stili, and` lightweight core-tor` the blade inY addition to defining cooling air passages.

By virtue ofthe invention, complicated forgings. or castings` are unnecessary and machiningofuthe blademay be greatly simplified. Thus,.the :cost of thebucken, the critical material requirements, and the production-difficulties of conventional buckets are greatly reduced. i

The nature otV the inventiomthe .advantages thereof, and the preferred manner in which the objects ofthe invention are realized will be apparent to those skilledin the art from the succeeding detailed' description of" the preferred embodiments of the invention and the accompanying'drawings, in which Fig. lisja longitudinalfsectionaliview'of a-turbineibucket mounted in a'fragment-ary portionlof a' turbine-wheel, the sectionwbeing"taken` ap= proximately on themean camberA linev ofY the blade; Figs. 2 and 3 are longitudinal sections of theisametaken on the planes indicated by the lines *,ZL-Zl'and 3-3,respectively, .inFi'g.-.1; Figs. d/.and` 5` are transversesections-of the. same takenwon .tha planesfindicated bytl'iedines 4 4 and 5-5, respectively, in Fig. l; Fig.. 6 is a transverse sectional view, cor-responding` to the section of Fig; 4, of a modiedlform of bucket; Fig. 7 isa longitudinal section ofathird form of bucket, this section being taken approximately on the mean camber line of the blade; Fig. 8 is a transverse section of the same taken on the plane indicated by the line E-Sin Fig. 7; and Figi 9- is a partial longitudinal section of the same taken on the plane indicated by the line 9-9 in Fig. 7.

Referring first to Figs. l to 5, the turbine bucket illustrated comprises a blade portion A and a base portion B mounted in a turbine wheel C which may be of conventional type. The wheel C is provided with` a conventional. multiple dovetail slot 11 extending across the rim of the wheel for mounting each bucket; The faces of the base or root B of the bucket are. formed with serrations 12 which engage in the grooves of the slot 11. The blade portion A may be of any suitable form dictated by the requirements of the installation. The blade form illustrated` is a typical one in which the ycrosssection of the blade is generally of ail-foil form, boththe chord and the thickness of the blade decrease away from the base, and the blademay be twisted, as will besmost ciearly apparentfrom Fig. 5. In short, the external configuration of the blade and root may be the same as conventional turbine buckets which may be replaced by the bucket of the invention.

The invention is also applicable to fixed or stator varies of turbines, compressors, and such,.in which :case a different configuration of the end or ends of the blade is ordinarily employed for mounting the huid-directing portion of the element. The Huid-directing faces of the blade extend from the leading edge13 to the trailing edge 14. The central part of the blade consists of a number of laminae stacked and brazedtogether' to form a unified structure. These laminae are of two types; laminae 16 shown in elevation in Fig. 2 which extend from face to face of the blade portion, the edges of these laminae thus defining elements of the fluid-directing surface of the blade, and laminae 17 shown in section in Fig. 2. These laminae comprise two parts 17a and 17b defining between them a channel 18 extending the length of the element to conduct a cooling medium such" as airffromethebase to the tipof the bucket. All of the laminae 16 and 17 continue from thebla-de portion into the base portion of the bucket, and their outer edges define elements of the side faces of the base B which are formed with the serrations 12.

It may be noted that the laminations have extension, or in` otherwords, extend, inthe directions lengthwisefof the blade and form face to face of the blade. This condition might also be dened by a .statementv that the laminaeA are perpendicular to a line extending generally chordwise of the blade. Specifically, as shown;` the laminae are-perpendicular to a line parallel to the direc; tion of the serrations 12'of the blade root.

The base also comprises end blocks 19 and 21 which form the ends ofthe blade root and have mounted b'etween them and have brazed thereto the base of the laminated structure; that is, the portions of laminae 16 and 17 between the end blocks. The base portion B of the bucket is formed to define an air chamber 22. between the ends thereof to which air may be supplied in any convenient manner as by passages 23 extending through the rim of the turbine wheel C. It will beepparent from Fig. 2 that the passages 18 communicate with the chamber 22. The laminae 16 are punchedto define a passage 24 extending lengthwise of the root interconnecting the passages 18; A

The/leading and trailing `edge portions 'of the blade (in advance of and behind thelaminatedstructure) are de.-`

nozzle blades fined by generally V-shaped sheet metalparts 27`and"28A "s which may be die-formed from sheet metal. These parts fit against the outermost laminae 16 and the upper face of the end blocks 19 and 21, and are brazed or welded thereto. The leading and trailing edge portions thus define air passages 3l, 32, also extending the length of the blade portion and being open at the tip of the blade. Air is conducted into these passages by slots 33 and 34 in the blocks 19 and 2li to which air is supplied through the passages 18 and 24.

As will be apparent, air introduced in any suitable way to the passage 23 will flow through this passage into chamber 22, through passages i8, and from passages i3 by cross-flow through passage 2d into passages 33 and 34, from which it flows through passages 3l and 32. As will be seen, the laminated structure braced together forms a very strong core or rigid central structure within the blade, the laminae 16 extending from face to face being particularly adapted to resist deflection of the blade and to provide extensive heat radiating surface scoured by the air flowing through the passages i3. nations may be relaitvely thin, the passages are of small width and highly ecient transfer of heat is accomplished.

Fig. 6 illustrates a modification of the bucket of Pig. l, which differs therefrom in that the leading and trailing edge portions 37 and 33 of the blade are solid strips of metal. Since this form does not provide as effective cooling of the leading and trailing edge portions of the bucket as the form of Fig. l, these parts must necessarily be of a more heat resistant material for the same service conditions and, ordinarily, may be cast or forged from any suitable highly heat resistant alloy such as those used for turbine buckets of conventional type. The end blocks 39 and 41 correspond to the end blocks 19 and 2li of Fig. l

but are not provided with the channels 33 and 34. The parts 37 and 39 may be integral and, likewise, the parts 38 and 41. The central or laminated part of the blade structure is substantially identical with that of Fig. l except that the outermost laminations are the divided laminations 17a and i719 to provide a flow of cooling air adjacent the parts 37 and 38.

Referring now to the third embodiment of the invention shown in Figs. 7, S, and 9, this form is similar in many respects to those previously described, differing notably in the fact that it is entirely of laminated construction. The central part of the balde and root may be identical with that of Fig. l but the leading and trailing edge portions of the blade and the ends of the blade root are formed by laminae which extend spanwise from the ,root and into the blade portion.

Parts similar to those already explained with reference to Figs. l to 5 are identified by the same reference characters as those applied to Figs. l to 5. immediately adjacent the foremost and rearmost laminations 17,

cooling channels 5l and Sil are defined within the blade as close as practicable to the leading and trailing edge. Laminae such as 52 which extend across the blad-c in the lower part of the blade is shown but are bifurcated toward the tip, and laminae such as 53 which are closed toward the tip of the blade but bifurcated nearer the base dene these passages. in addition, to increase the size of the channel, laminae 54 which are open at both ends and thus are substantially the same as laminae 1'7 may be provided between the laminae 52 and 533. The foremost and rearmost laminae identified as Se extend completely across the blade root to Seal off the ends of the root and may extend slightly into the blade portion where it fairs into the base.

This form of bucket offers the advantages of a com-- pletely laminated construction but is not as Welladapted to .cooling as the form of Fig. l, and not as well adapted ot resist heat as the form of Fig. 6. Y

The method of manufacturing parts of the buckets, assembling them, and unifying them by brazing or the like, need not be described in detail since thc procedure Since the lamitit) may follow that described in our companion case S. N. 292,545 filed lune 9, 1952, entitled Turbine Buckets. Our application S. N. 292,547, tiled June 9, i952 contains subject matter related to that of this application.

Since the laminated structure assembled from sheet metal stampings is rough, it is necessary to grind or otherwise machine the srrface to provide the necessary smoothness and accuracy of the airfoil surface. ln the form of Figs. l and 6 this machining could be limited to the central part of the surface which is the easiest to contour. in any event, the very ample provision for cooling of the bucket and the high strength of the bucket with relation to its weight permit the usc of more tractablc materials so that the finishing is less difficult than with alloys such as are commonly used for gasturbine buckets.

The advantages of the invention in providing a strong and heat resistant structure with excellent heat transfer characteristics and adaptability to production will be apparent to those skilled in the art. it may be noted that the stepped contour of the inner wall of the bucket where it defines the passages 51 and 5t) considerably increases the heat transfer surface over that which would be provided by a smooth surface and, of course, the laminae extending entirely across the bucket provided a high ratio of heat transfer surface to the heat absorbing outer surface of the blade.

ln order to explain the principles of the invention, preferred embodiments thereof have been described in detail. lt should be understood, however, that this descrip tion is not tol be regarded as limiting the invention, as many modifications thereof may be devised by skill in the art Within the principles and scope of the invention.

We claim:

l. A fluid-directing blade for turbomachines and the like, said blade having fluid-directing faces and comprising a number of physical united laminae extending in the directions lengthwise of the blade and from face to face of the blade, the edges of the laminae constituting elements of the uid-directing faces of the blade, some of said laminae extending from face to face of the blade and others of said laminae being open through the center of said other laminae to define passages extending longitudinally of the blade, all of said laminae extending heyond one end of said huid-directing faces to provide means for attaching the blade to a supporting structure, the chord of the blade decreasing from the said one end, the said laminae including laminae adjacent one edge of the blade being open at the said one end and being closed at progressively increasing distances from the other end to define one side of a passage generally parallel to the said edge of the blade. K

2. A fluiddirecting blade for turbomachines and the like, said blade having fluid-directing faces andpcomprising a number of physically united laminae each having extension in the directions lengthwise of the blade and from face to face of the blade, the edges of theI laminae constituting elements of the fluid directing faces of the blade, some of said laminae, constituting a rst set, extending unbroken from face to face of the blade, and others of said laminae, constituting a second set, defining openings through the centers of said other laminae extending lengthwise of the blade from end to end thereof providing passages extending longitudinally of the blade from end to end thereof, the laminae of the two sets `alternating chordwise of the blade. n

3. A fluid-directing blade as recited in claim 2 in which the said united'laminae define the duid-directing faces only over the central part of the blade chordwise and the said faces include leading edge and trailing edge portions dened by continuous members of substantially greater chordwise extent than a said lamina mounted on the said united laminae. f i

4. A fluid-directing blade as recited in claim 3 in which the said members are of sheet metal of channel form and dene air conduits within the leading and trailing edges of the blade.

5. A Huid-directing blade as recited in claim 2 in which the said united laminae dene the duid-directing faces only over the central part of the blade chordwise and the said faces include leading edge and trailing edge portions defined by continuous members mounted on the said united laminae, the said continuous members being solid and of substantially greater chordwise extent than a said lamina and being composed of a highly heat-resistant alloy.

6. A fluid-directing blade as recited in claim 2 in which the entire blade is of laminated construction.

7. A fluid-directing blade for turbomachines and the like, said blade having Huid-directing faces and comprising a number of physically united laminae each having extension in the directions lengthwise of the blade and from face to face of the blade, the edges of the laminae constituting elements of the liuid directing faces of the blade, some of said laminae, constituting a lirst set, ex `tending unbroken from face to face of the blade, and others of said laminae, constituting a second set, defining openings through the centers of said other laminae extending lengthwise of the blade from end to end thereof providing passages extending longitudinally of the blade from end to end thereof, the laminae of the two sets alternating chordwise of the blade, all of said laminae extending beyond one end of said fluid-directing faces and providing a blade root for attaching the blade to a supporting structure.

8. A iiuid-directing blade as recited in claim 7 in which the said united laminae define the fluid-directing faces only over the central part of the blade chordwise and said faces include leading edge and trailing edge portions dened by continuous members of substantially greater chordwise extent than a said lamina mounted on the said united laminae.

9. A Huid-directing blade as recited in claim 8 in which the said members are of sheet metal of channel form and define air conduits within the leading and trailing edges of the blade.

10. A fluid-directing blade as recited in claim 7 in which the said united laminae dene the fluid-directing faces only over the central part of the blade chordwise and said faces include leading edge and trailing edge portions defined by continuous members mounted on the said united laminae, the said continuous members being solid and of substantially greater chordwise extent than a said lamina and being composed of a highly heat-re sistant alloy.

11. A duid-directing blade as recited in claim 7 in which the entire blade is of laminated construction.

12. A duid-directing member for turbomachines and the like, said member comprising a blade portion having faces for directing fluid and an adjacent base portion for mounting the member, the member comprising a number of physically united laminae each having extension in the directions lengthwise of the blade portion and from face to face of the blade portion, the edges of the laminae constituting elements of the Huid-directing faces of the blade portion, some of said laminae extending unbroken from face to face of the blade portion and others of said laminae defining openings through the centers of said other laminae extending lengthwise of the blade portion from end to end thereof constituting passages extending longitudinally of the blade portion from end to end thereof, all of said laminae extending beyond one end of said blade portion into the base portion and constituting at least part of the base portion.

13. A tiuid-directing member as recited in claim 12 in which the said united laminae define the fluid-directing faces only over the central part of the blade chordwise and the said faces include leading edge and trailing edge portions defined by continuous members of substantially greater chordwise extent than a said lamina mounted on the said united laminae.

14. A duid-directing member as recited in claim 13 in which the said members are of sheet metal of channel form and dene air conduits within the leading and trail* ing edges of the blade.

15. A fluid-directing member as recited in claim l2 in which the said united laminae define the fluid-directing faces only over the central part of the blade chordwise and the said faces include leading edge and trailing edge portions defined by continuous members mounted on the said united laminae, the said continuous members being solid and of substantially greater chordwise extent than a said lamina and being composed of a highly heatresistant alloy.

16. A duid-directing member as recited in claim 12 in which the entire blade portion is of laminated construction.

17. A fluid directing member for turbomachines and the like, said member comprising a blade portion having faces for directing iiuid and an adjacent base portion for mounting the member, the member comprising a number of physically united laminae each having extension in the directions lengthwise of the blade portion and from face to face of the blade portion, the edges of the laminae constituting elements of the duid-directing faces of the blade portion, some of said laminae extending unbroken from face to face of the blade portion and others of said laminae defining openings through the centers of said other laminae extending lengthwise of the blade portion from end to end thereof constituting passages extending longitudinally of the blade portion from end to end thereof, all of said laminae extending beyond one end of said blade portion into the base portion and constituting at least part of the base portion, the edges of the laminae in the base portion being formed to engage in a supporting structure.

References Cited in the file of this patent UNITED STATES PATENTS 2,613,058 Atkinson Oct. 7, 1952 2,618,462 Kane NOV. 18, 1952 FOREIGN PATENTS 647,143 Great Britain Dec. 6, 1950 

